Guest Trapdoor2 Posted October 7, 2013 Share Posted October 7, 2013 Installing replacement carb today...very nice unit from CarbExchange. Slight differences from my original carb, the dashpot lever is further out from the carb body...no big deal. Old out and new in, took about an hour. Check and double check. Everything hooks up perfectly, no worries. I call Miz Diane out to start her up while I monitor the engine compartment. Got to teach her the drill first. Key in switch, turn to "on", step on throttle, etc.Except the throttle wouldn't return when she stepped on it (starter engaged). Bright girl, she hooked the pedal with her sandal and pulled. Throttle returned with a snap. Hmmmmm. Try again...same result.Ok, I drop the attempt to start and start solving throttle linkage problem (Miz Diane retreats back in the house). The linkage works normally until I get to about 60% (just a guess) and then sort of feels like it goes "over center" and sticks...almost wide open. I can tap the throttle arm (on the carb) and it will return properly. Just takes a little push to get it to come back...but more than the throttle return spring can handle. I rigged up a hook for the throttle return spring that is further away (adding some "pull" to the spring) but it isn't enough to pull the throttle shut once it is past that magic "over center" point.Of course, the whole system is buried back behind the engine. Tired, sore, hot and grumpy after a couple hours, I give up for the evening.I simply couldn't find anything wrong. It wasn't binding or sticking prior to the carb swap. Now, even if I disconnect the throttle link (off the carb), the damn thing still sticks. The throttle "stretch link" spring is broken...but it was broken prior to the carb swap.I know the stator op rod is involved with this system...I'm wondering if there is some sort of interaction going on that I'm missing (or simply too green to suss out). I'm reading the shop manual and looking at the pix (posted here on another thread) of the throttle linkage system. I haven't pulled up the carpet behind the pedal (and yes, the boot is long gone) yet.Any help? Link to comment Share on other sites More sharing options...
JohnD1956 Posted October 7, 2013 Share Posted October 7, 2013 I wonder if the link between the primaries and secondaries is installed backwards/ upside down? It's hard to get a picture of this assembly and it may be that it's impossible to install them incorrectly. But there is a lockout tang which should prevent WOT when the choke is not fully open. MAybe the linkage is hanging up on that? Link to comment Share on other sites More sharing options...
Guest Trapdoor2 Posted October 7, 2013 Share Posted October 7, 2013 The problem is the linkage between the carb and the gas pedal. All the linkage on the carb itself functions normally. I gave everything I could see a good hosing with WD-40. Tonight I'm going to leave the carb unhooked from the gas-pedal (at least, I think I can start it by working the carb manually, the vacuum start switch is right there...and working) and get her running. Of course, I probably need to put her up on jacks, crawl underneath and see what I can see. If I can get her running, I may (gently) drive her down to the local self-serve garage and rent an hour or two on one of their lifts ($25/hr). That was in the plan anyway before all this happened. Link to comment Share on other sites More sharing options...
JohnD1956 Posted October 8, 2013 Share Posted October 8, 2013 If the dash pot tab is too far out, then the hook up for the throttle is probably too far out too. On my 56 Rochester 4GC carb they are one piece. On my 56 the throttle rod is on the ball on the outside of the carb linkage. If yours is on the outside too, and it is too far out, it may be binding when the rod passes 3/4 mark on the linkage where the ball is. Maybe you need to reverse the ball and move the throttle rod to the inside between the carb and the tab which hold the ball? I hope this makes some sense. Can you post a picture of the set up? Link to comment Share on other sites More sharing options...
Guest Trapdoor2 Posted October 19, 2013 Share Posted October 19, 2013 Well! After a week of not working on the Buick, I finally got two minutes to rub together and sorted out the sticky throttle linkage problem!Lesson #1: get a good light. I have a fluorescent drop light...which is about as effective as using a bottle of dead fireflies. I picked up one of those 100w LED headband flashlights at Lowe's last week and Holy Cannoli, I saw the problem right away.The large steel vacuum line which connects to the front of the intake manifold and runs back past the carb (on the linkage side) had to be moved aside about 1/4" to clear the dashpot tab on the new carb linkage. When I repositioned the line, I evidently moved part of it which ducks behind the engine...and it was jamming up the throttle just enough for it to hang at around 60% open.With the new headlamp, and the throttle linkage disconnected at the carb, I was able to sit there and work it back and forth while watching...and saw the vacuum line moving. AHA! I got out my trusty extendable mirror and was able to just see the issue. I re-repositioned the line and voila!Once I had a nice, smooth throttle linkage, I hooked everything up, poured a bit of gas down her brand-new-rebuilt-and-tested carb...Vaarrrooooom!I took her for a test drive and boy-oh-boy, what a difference! Drives like she ought to. Now I got to put the reconditioned vacuum advance on her and aaa-wayyy we go!===Marc Link to comment Share on other sites More sharing options...
JohnD1956 Posted October 23, 2013 Share Posted October 23, 2013 Nice work... Link to comment Share on other sites More sharing options...
bhambulldog Posted October 24, 2013 Share Posted October 24, 2013 Hooray!!!!Nice Work!! Link to comment Share on other sites More sharing options...
Guest Trapdoor2 Posted October 27, 2013 Share Posted October 27, 2013 This was a quick one, albeit a bit of shade-tree engineering involved.The throttle 'stretch link' has been an obvious issue since I bought the car. For those who don't have one, this is a spring loaded rod running from the firewall throttle lever to the carb. At least it is supposed to be spring loaded. Para. 3-9 of the '55 shop manual describes the adjustment of the stretch link, depending on whether the vehicle is set up for overtravel or without overtravel. As far as I can tell, the only difference is whether WOT is limited by the stop screw on the carb or by the pedal hitting the floor mat. Seriously? Hitting the floor mat? Para 3-9a.14 sez so. The stretch link becomes involved if you wish to use the carb stop screw as a limit...then when you hit WOT, the stretch link stretches so you don't break anything with yer big damn feet. Since I got my carb and vacuum advance problems solved, driving the Buick has been almost a pleasure. "Almost" because the stupid broken stretch link was making throttle operation a "hit or miss" issue. The pedal had to be depressed a long way to get things going and then when you stopped accelerating, you had to almost completely back off the pedal before the throttle would close. The throttle would not return to idle at the same spot (rpm) twice in a row. It might sit and burble at one stop light, the next it would leap off the line.So, today I decided to sort out the 'stretch link'. I remove it from the vehicle and start looking it over while it is sitting on the fender-pad. The silly thing has a crimped-on hexagonal cover, there must be a spring inside. Someone has wrapped one end (the firewall end) of this cover with old copper wire (like household ground wire). I unwrap the wire and that end spreads open...the rod in that end is held in place by two small tangs on the rod that fit into two holes in the cover. Once you split the cover, the rod can drop out.With the firewall-end of the rod out, I can see into the spring cover...looks like threads but I can't see very far in. With a pair of pliers, I start gently peeling open the crimps on the cover. When I can open the cover a bit, I see that there is a nut captured by the hexagonal form of the cover...and that the other end of the link rod screws into this nut...and there's a spring in there. I twist the link rod (this is the carb end) and thread it into the nut...voila! The rod is now spring loaded! Sheesh. Too simple.Now I gotta put it all back together. The hexagonal cover part is pretty soft sheet-metal and it has been distorted over time. Even with the crimps back in place, the firewall side rod isn't exactly held in place very well, thus the copper wire wrapping. A tiny Jubilee clamp would probably be the best fix. Not having one, I got out my trusty 0.032 safety wire (from when I was an A&P aircraft mechanic) and wired it down tight.Now the 'stretch link' stretches as it ought to...and it is solid in compression. It was gaining 1/2" in length under tension (acceleration) and then not completely coming back together when the throttle pedal was free. Now, properly adjusted, the car drives like it should...pure pleasure. For the first time since I've had it, I feel confident that my wife can now drive it...which is why we bought it in the first place.Woo hoo! Link to comment Share on other sites More sharing options...
bhambulldog Posted October 28, 2013 Share Posted October 28, 2013 Nice work Marc ! Link to comment Share on other sites More sharing options...
old-tank Posted October 28, 2013 Share Posted October 28, 2013 Good job...gotta love that trusty 0.032 safety wire. Link to comment Share on other sites More sharing options...
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